Change in Soil Erosion by Wind on Cropland and CRP Land, 1992 - 1997

Description

This shaded polygon map shows the change in the average annual rate of soil erosion by wind in tons per acre per year on cropland and Conservation Reserve Program (CRP) land between 1992 and 1997. The average annual Wind Erosion Equation (AAWEQ) is used to determine annual erosion rates. Data are aggregated by 8-digit hydrologic unit areas. Areas where cropland and CRP land occupy less than 5% of the total area are hatched. Areas with 95% or more Federal area are shaded gray. There was a net decrease of 0.2 tons per acre per year between 1992 and 1997.

Cautions for this Product:
Since cropland and CRP land may occupy only a small percentage of the total area of some of the polygons, the map may leave a misleading impression as to the higher erosion rates in some areas. Data are not shown where cropland and CRP are less than 5% of the total area. Data are not collected on Federal land. Data are not available for Alaska or the Pacific Basin. Data for Puerto Rico and the U.S. Virgin Islands is shown by 6-digit hydrologic unit.

Sources

Source:National Resources Inventory, 1997Distributor: USDA-NRCS-RIADReliability:
NRI sample data are generally reliable at the 95% confidence interval for state and certain broad substate area analyses. Generally, analyses that aggregate data points by smaller geographic areas and/or more specific criteria result in fewer data points for each aggregation and therefore less reliable estimates. NRI maps reflect national patterns rather than site- specific information.

Layers

Definitions

Conservation Reserve Program (CRP):
A Federal program established under the Food Security Act of 1985 to assist private landowners to convert highly erodible cropland to vegetative cover for 10 years. [NMCSP]

Cropland:
A Land cover/use category that includes areas used for the production of adapted crops for harvest. Two subcategories of cropland are recognized: cultivated and noncultivated. Cultivated cropland comprises land in row crops or close-grown crops and also other cultivated cropland, for example, hayland or pastureland that is in a rotation with row or close-grown crops. Noncultivated cropland includes permanent hayland and horticultural cropland. [NRI-97]

Erosion:
The wearing away of the land surface by running water, waves, or moving ice and wind, or by such processes as mass wasting and corrosion (solution and other chemical processes). The term "geologic erosion" refers to natural erosion processes occurring over long (geologic) time spans. "Accelerated erosion" generically refers to erosion that exceeds what is presumed or estimated to be naturally occurring levels, and which is a direct result of human activities (e.g., cultivation and logging). [NSSH-96]

Wind erosion:
The process of detachment, transport, and deposition of soil by wind. [NAM]

Wind erosion equation (WEQ):
An erosion model designed to predict long-term average annual soil losses from a field having specific characteristics (NAM). E= f(IKCLV) where E is the estimated average annual soil loss expressed in tons per acre per year; I is the soil erodibility; K is the soil ridge roughness factor; C is the climatic factor; L is the equivalent unsheltered distance across the field along the prevailing wind erosion direction; and V is the equivalent vegetative cover. [NAM]